refactor: improve CandidatesView's positioning

Author: WhiredPlanck

app/src/main/java/com/osfans/trime/ime/composition/CandidatesView.kt

@@ -40,6 +40,7 @@ import splitties.views.dsl.core.withTheme
 import splitties.views.dsl.core.wrapContent
 import splitties.views.horizontalPadding
 import splitties.views.verticalPadding
+import kotlin.math.roundToInt
 
 @SuppressLint("ViewConstructor")
 class CandidatesView(
@@ -59,11 +60,20 @@ class CandidatesView(
 
     private var shouldUpdatePosition = false
 
+    /**
+     * layout update may or may not cause [CandidatesView]'s size [onSizeChanged],
+     * in either case, we should reposition it
+     */
     private val layoutListener =
         OnGlobalLayoutListener {
             shouldUpdatePosition = true
         }
 
+    /**
+     * [CandidatesView]'s position is calculated based on it's size,
+     * so we need to recalculate the position after layout,
+     * and before any actual drawing to avoid flicker
+     */
     private val preDrawListener =
         OnPreDrawListener {
             if (shouldUpdatePosition) {
@@ -103,33 +113,37 @@ class CandidatesView(
             menu.candidates.isNotEmpty()
 
     private fun updateUi() {
+        preeditUi.update(inputComposition)
+        preeditUi.root.visibility = if (preeditUi.visible) View.VISIBLE else View.INVISIBLE
+        // if CandidatesView can be shown, rime engine is ready most of the time,
+        // so it should be safety to get option immediately
+        val isHorizontalLayout = rime.run { getRuntimeOption("_horizontal") }
+        candidatesUi.update(menu, isHorizontalLayout)
         if (evaluateVisibility()) {
-            preeditUi.update(inputComposition)
-            preeditUi.root.visibility = if (preeditUi.visible) View.VISIBLE else View.INVISIBLE
-            // if CandidatesView can be shown, rime engine is ready most of the time,
-            // so it should be safety to get option immediately
-            val isHorizontalLayout = rime.run { getRuntimeOption("_horizontal") }
-            candidatesUi.update(menu, isHorizontalLayout)
             visibility = View.VISIBLE
         } else {
+            // RecyclerView won't update its items when ancestor view is GONE
+            visibility = View.INVISIBLE
             touchEventReceiverWindow.dismiss()
-            visibility = GONE
         }
     }
 
     private fun updatePosition() {
-        val x: Float
-        val y: Float
-        val (horizontal, top, _, bottom) = anchorPosition
+        if (visibility != View.VISIBLE) return
         val (parentWidth, parentHeight) = parentSize
         if (parentWidth <= 0 || parentHeight <= 0) {
             translationX = 0f
             translationY = 0f
             return
         }
-        val selfWidth = width.toFloat()
-        val selfHeight = height.toFloat()
+        val (horizontal, top, _, bottom) = anchorPosition
+        val w = width
+        val h = height
+        val selfWidth = w.toFloat()
+        val selfHeight = h.toFloat()
 
+        val x: Float
+        val y: Float
         val minX = 0f
         val minY = 0f
         val maxX = parentWidth - selfWidth
@@ -165,9 +179,7 @@ class CandidatesView(
         translationX = x
         translationY = y
         // update touchEventReceiverWindow's position after CandidatesView's
-        if (evaluateVisibility()) {
-            touchEventReceiverWindow.showup()
-        }
+        touchEventReceiverWindow.showAt(x.roundToInt(), y.roundToInt(), w, h)
         shouldUpdatePosition = false
     }
 
@@ -183,7 +195,7 @@ class CandidatesView(
     }
 
     init {
-        visibility = View.GONE
+        visibility = View.INVISIBLE
 
         minWidth = dp(theme.generalStyle.layout.minWidth)
         minHeight = dp(theme.generalStyle.layout.minHeight)

app/src/main/java/com/osfans/trime/ime/composition/PreeditModule.kt

@@ -71,7 +71,7 @@ class PreeditModule(
         ui.update(ctx.composition)
         ui.root.visibility = if (ui.visible) View.VISIBLE else View.INVISIBLE
         if (ctx.composition.length > 0) {
-            touchEventReceiverWindow.showup()
+            touchEventReceiverWindow.show()
         } else {
             touchEventReceiverWindow.dismiss()
         }

app/src/main/java/com/osfans/trime/ime/composition/PreeditUi.kt

@@ -70,20 +70,19 @@ open class PreeditUi(
         str: CharSequence,
         visible: Boolean,
     ) = preedit.run {
-        if (visible) {
-            text = str
-            if (visibility == View.GONE) visibility = View.VISIBLE
-        } else if (visibility != View.GONE) {
-            visibility = View.GONE
-        }
+        text = str
+        visibility = if (visible) View.VISIBLE else View.GONE
     }
 
     fun update(inputComposition: RimeProto.Context.Composition) {
         val string = inputComposition.toSpannedString()
         val cursorPos = inputComposition.cursorPos
         val hasPreedit = inputComposition.length > 0
         visible = hasPreedit
-        if (!visible) return
+        if (!visible) {
+            updateTextView("", false)
+            return
+        }
         val stringWithCursor =
             if (cursorPos == 0 || cursorPos == string.length) {
                 string

app/src/main/java/com/osfans/trime/ime/core/TouchEventReceiverWindow.kt

@@ -31,20 +31,29 @@ class TouchEventReceiverWindow(
 
     private val cachedLocation = intArrayOf(0, 0)
 
-    fun showup() {
+    fun showAt(
+        x: Int,
+        y: Int,
+        w: Int,
+        h: Int,
+    ) {
         isWindowShowing = true
-        val (left, top) = cachedLocation.also { contentView.getLocationInWindow(it) }
-        val width = contentView.width
-        val height = contentView.height
         if (window.isShowing) {
-            window.update(left, top, width, height)
+            window.update(x, y, w, h)
         } else {
-            window.width = width
-            window.height = height
-            window.showAtLocation(contentView, Gravity.NO_GRAVITY, left, top)
+            window.width = w
+            window.height = h
+            window.showAtLocation(contentView, Gravity.TOP or Gravity.START, x, y)
         }
     }
 
+    fun show() {
+        val (x, y) = cachedLocation.also { contentView.getLocationInWindow(it) }
+        val width = contentView.width
+        val height = contentView.height
+        showAt(x, y, width, height)
+    }
+
     fun dismiss() {
         if (isWindowShowing) {
             isWindowShowing = false